1. Field of the Invention
The present invention relates to a communication relay device, a communication system, and a communication control program for relaying transmission and reception of information between an inside network and an outside network.
2. Description of the Related Art
The products called digital information home electronics are becoming popular. These products are expected to become even more popular in conjunction with the start of the digital broadcasting, and include all kinds of products for handling digital data and digital contents such as digital broadcasting compatible TV, set-top box, digital VTR, DVD player, hard disk recorder, etc.
The quality of the digital data and digital contents will not be degraded even when they are copied, and the copies can be made easily, so that there is a need to provide a measure for the copyright protection in advance. For example, in the IEEE 1394 which is a digital network for connecting digital AV devices, the authentication and key exchange mechanism and the data encryption function are provided.
Here, consider a case of transferring the AV data that requires the copyright protection, from some transmission device. What needs to be taken into consideration here is that the copyright protection presupposes to allow the exchange of the AV data within a range of personal (or family) entertainment, but to prevent the exchange of the AV data with a third person (unless the permission from the copyright holder is given).
A known mechanism for realizing the copyright protection on a network includes DTCP (Digital Transmission Content Protection), which is a copyright protection scheme that has become de facto standard in IEEE 1394 and USB.
The DTCP is provided with a mechanism for carrying out the authentication and key exchange between a transmission device and a reception device and transferring the AV data by encrypting them, with respect to contents such as the AD data that require the copyright protection (see documents disclosed at “http://www.dtla.com”, for example). By using this DTCP, it becomes possible to transmit the AV data in a state that guarantees the copyright protection, on an inside network (IEEE 1394 network, for example).
On the other hand, in conjunction with the spread of the internet, it has become customary to exchange the digital data on a public network. Under such a circumstance, there can be cases where a user requests an access to the data maintained at the user's home in a mobile environment, as in a case of access from the user's villa. If such a request is to be rejected for the reason of the copyright protection, the user's convenience would be severely damaged.
However, the current DTCP has its application target limited to home networks such as IEEE 1394. In order to make it possible for a user to make an access to the contents maintained at the user's home in the mobile environment, there is a need to expand the current DTCP such as it can be used outside as well, and to expand the mechanism realized by the inside DTCP to the outside, but there has been no proposition for such a new mechanism conventionally.